1. Field of the Invention
The present invention relates generally to power controlling technologies in a communication system, and more particularly, to a method for controlling Uplink (UL) power in a cell using a multi-subframe scheduling.
2. Description of the Related Art
A Long Term Evolution (LTE) system of the 3rd Generation Partnership Project (3GPP) standardization organization may support two duplex modes, that is, Frequency-Division Duplexing (FDD) and Time-Division Duplexing (TDD). For the foregoing two modes, length of each radio frame is 10 ms. Each radio frame may consist of 10 subframes, the length of which is 1 ms. The subframe may consist of two consecutive time slots, the length of which is 0.5 ms. That is, a kth subframe includes time slots 2k and (2k+1).
For an LTE FDD system, Uplink and Downlink (UL-DL) transmissions may be implemented with two symmetric bands. Thus, at each moment, a UL subframe and a Downlink (DL) subframe may exist simultaneously. For an LTE TDD system, UL-DL transmissions may be implemented with one band, which may be differentiated with time. That is, based on different configurations, different subframes in one system frame may be respectively defined as a UL subframe, a DL subrame, a special subframe (that is, a subframe consisting of a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP) and an Uplink Pilot Time Slot (UpPTS)). The existing LTE TDD system may support 7 kinds of UL-DL configurations, as shown in Table 1. In Table 1, “D” represents a DL subframe, “U” represents a UL subframe, and “S” represents a special subframe.
TABLE 1LTE TDD UL-DL configurationsconfigurationconversionsequencepointsubframe numbernumberperiod01234567890 5 msDSUUUDSUUU1 5 msDSUUDDSUUD2 5 msDSUDDDSUDD310 msDSUUUDDDDD410 msDSUUDDDDDD510 msDSUDDDDDDD610 msDSUUUDSUUD
In an LTE system, the UL-DL transmission may be implemented with scheduling of an evolved Node B (eNB).
For a DL transmission, an eNB may transmit a DL scheduling command for a certain UE via a Physical Downlink Control CHannel (PDCCH)/an Enhanced PDCCH (EPDCCH) in a DL subframe n. The corresponding UE may receive Physical Downlink Shared CHannel (PDSCH) data in subframe n, based on the DL scheduling instruction of the PDCCH/EPDCCH data. The corresponding UE may also feed back the Acknowledge (ACK)/Negative ACK (HACK) of the PDSCH data via a Physical Uplink Control CHannel (PUCCH) or Physical Uplink Shared CHannel (PUSCH) of an uplink subframe (n+k). For an FDD system, the value of k is always 4. For a TDD system, value of k is dependent on the UL-DL configurations of the TDD, as shown in Table 2.
TABLE 2Values of k corresponding to different TDD UL-DL configurationsconfigurationsequencesubframe number nnumber0123456789046———46———176———76—44276—4876—483411———7665541211——87765451211—98765413677———77——5
For the UL transmission, an eNB may transmit a UL scheduling command for a certain UE via a PDCCH/EPDCCH in the DL subframe n. The corresponding UE may transmit PUSCH data in a UL subframe n+KPUSCH, based on the UL scheduling instruction in the PDCCH/EPDCCH data. For an FDD system, the value of KPUSCH is always 4. For a TDD system, the value of KPUSCH is dependent on the UL-DL configurations of TDD, as shown in Table 3.
TABLE 3Values of KPUSCH corresponding to different TDD UL-DL configurationsconfigur-ationsequenceDL subframe index nnumber012345678904, 76, 74, 76, 716464244344444454677775
In the existing LTE/LTE-Advanced (LTE-A) system, transmitting power of a UL subframe may be dynamically controlled by an eNB. The eNB may inform a UE about UL power controlling parameters of static and semi-state, by using a broadcast message and a Radio Resource Control (RRC) layer message. In each UL subframe, a UE may determine the transmitting power of the PUSCH, and/or PUCCH of a current subframe, by using these UL power controlling parameters and a power controlling instruction, which was received via the PDCCH/EPDCCH previously.
For example, when PUSCH data and PUCCH data are not transmitted via a same UL subframe, the power of PUSCH of subframe i in current cell c may be determined by using Equation (1).
                                          P                          PUSCH              ,              c                                ⁡                      (            i            )                          =                  min          ⁢                                    {                                                                                                                                            P                                                      CMAX                            ,                            c                                                                          ⁡                                                  (                          i                          )                                                                    ,                                                                                                                                                          10                        ⁢                                                                              log                            10                                                    ⁡                                                      (                                                                                          M                                                                  PUSCH                                  ,                                  c                                                                                            ⁡                                                              (                                i                                )                                                                                      )                                                                                              +                                                                        P                                                      O_PUSCH                            ,                            c                                                                          ⁡                                                  (                          j                          )                                                                    +                                                                                                    α                            c                                                    ⁡                                                      (                            j                            )                                                                          ·                                                  PL                          c                                                                    +                                                                        Δ                                                      TF                            ,                            c                                                                          ⁡                                                  (                          i                          )                                                                    +                                                                        f                          c                                                ⁡                                                  (                          i                          )                                                                                                                                ⁢                                                          }                        ⁡                          [              dBm              ]                                                          (        1        )            
When accumulation is active, fc(i)=fc(i−1)+δPUSCH,c(i−KPUSCH). When the accumulation is inactive, fc(i)=δPUSCH,c(i−KPUSCH). δPUSCH,c is a power controlling command value, which is in a UL scheduling instruction used for scheduling a UL subframe i, or in a Downlink Control Information (DCI) format 3/3 A of the UE. The specific meanings of other physical parameters may be found by referring to 3GPP protocol 36.213.
The power of PUCCH of subframe i in current cell c may be determined by using Equation (2).
                    ⁢          (      2      )                          P        PUCCH            ⁡              (        i        )              =          min      ⁢                        {                                                                                                                P                                              CMAX                        ,                        c                                                              ⁡                                          (                      i                      )                                                        ,                                                                                                                          P                    O_PUCCH                                    +                                      PL                    c                                    +                                      h                    ⁡                                          (                                                                        n                          CQI                                                ,                                                  n                          HARQ                                                ,                                                  n                          SR                                                                    )                                                        +                                                            Δ                      F_PUCCH                                        ⁡                                          (                      F                      )                                                        +                                                            Δ                      TxD                                        ⁡                                          (                                              F                        ′                                            )                                                        +                                      g                    ⁡                                          (                      i                      )                                                                                                    ⁢                                          }                ⁡                  [          dBm          ]                    
In Equation (2),
      g    ⁡          (      i      )        =            g      ⁡              (                  i          -          1                )              +                  ∑                  m          =          0                          M          -          1                    ⁢                                    δ            PUCCH                    ⁡                      (                          i              -                              k                m                                      )                          .            δPUCCH is a power controlling command value, which is in a DL scheduling instruction used for scheduling a DL subframe i−km, or in the DCI format 3/3 A of the UE. For the FDD system, M=1, k0=4. For the TDD system, the values of M and km are as shown in Table 4. The specific meanings of each physical parameter may be found by referring to 3GPP protocol 36.213.
TABLE 4Indexes {k0, k1, . . . kM−1} of a binding relationship between a DL subframe and a UL subframe in a TDD systemconfiguration sequence subframe number nnumber01234567890——6—4——6—41——7, 64———7, 64—2——8, 7, 4, 6————8, 7,——4, 63——7, 6, 116, 55,—————44——12, 8, 7, 6, 5,——————114, 75——13, 12, 9, ———————8, 7, 5, 4, 11, 66——775——77—
Accompanying the increasing data rate requirements put forward by users, in LTE-A, multi-subframe scheduling technologies are becoming more and more focused. In the multi-subframe scheduling, one scheduling instruction may simultaneously schedule multiple DL subframes, or multiple UL subframes. That is, the scheduling instruction and scheduled subframe are no longer in a one to one correspondence. As shown in FIG. 1, by using the multi-subframe scheduling technologies, resource overheads of scheduling instructions may be saved. In addition, since there is no sufficient resource for some special subframes to transmit a UL scheduling command, a UL subframe corresponding to the DL subframe may not be scheduled. The foregoing problem may be well solved, by using the multi-subframe scheduling technologies.
However, a new problem about UL power controlling may be introduced by the multi-subframe scheduling. As mentioned above, based on a definition of the existing standard, the power of PUSCH of a certain UL subframe may be controlled by a power controlling command, which is in a UL scheduling command of a corresponding DL subframe, or is in the DCI format 3/3 A of the UE. The power of PUCCH of a certain UL subframe may be determined by a DL scheduling command, which is in a DL subframe bound with the UL subframe, or may be determined by a scheduling command in the DCI format 3/3A of the UE. However, in the multi-subframe scheduling, the foregoing corresponding relationship may be disorganized. Thus, it is necessary to re-design the power controlling method of the PUSCH and PUCCH, based on the characteristics of the multi-subframe scheduling.
Based on foregoing analysis, it can be seen that a new problem regarding power controlling of PUSCH and PUCCH may be brought about by multi-subframe scheduling. At present, there is no effective method to solve this problem.